Optimisation of the hull steel weight considering ice class for the design of an electric ferry
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Journal Title
Journal ISSN
Volume Title
Insinööritieteiden korkeakoulu |
Master's thesis
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Author
Date
2024-08-19
Department
Major/Subject
Ocean Structure
Mcode
Degree programme
Nordic Master Programme in Maritime Engineering
Language
en
Pages
69+63
Series
Abstract
Alternative propulsion systems are becoming increasingly important in the maritime industry due to climate change. For this reason, the FUSE project aims to reduce CO2 emissions by investigating design options for electric RoPax vessels. For vessels in this order of magnitude, the power requirement for the engine needs to be reduced in order to minimise the demand on batteries. Therefore, one key challenge of the project is to reduce the mass of the vessel. In this context, ice-going ships have a significant proportion of the steel weight located in the ice belt. This offers the opportunity to reduce weight at this point. This thesis deals with the optimisation of the ice belt structure to answer the question if steel weight can be significantly reduced by lowering the ice class and accounting for recent data of ice conditions. It also considers possible compromises that a ship owner would have to accept when reducing the ice class. In addition, the effect of the steel grade on the steel weight of the ice belt is discussed. The structural analysis of the ice belt is realised by using a parametric finite element model, which is created with the software Abaqus. The ice load is applied according to the Finnish-Swedish Ice Class Rules, which are based on an elastic limit state. The steel structure is optimised using a Particle Swarm Optimisation (PSO). The PSO is carried out in three optimisation steps, which are referred to as the ice class study, the ice condition study and the steel grade study. The results of the PSO are compared with an analytical approach. This method is applied to the case study of an electric ferry. The results indicate that the steel weight reduction is more efficient for a steel structure with the highest ice class IA Super and the lowest steel grade S235. By lowering the ice class, it is possible to save up to 17.0 % of the ice belt steel weight and 1.57 % of the total steel weight. When the steel grade is increased, the percentage rates of mass reduction correspond to 22.8 % and 2.57 % respectively. Another result is that a ship with an ice class IB cannot operate on the ferry route for 0.8 % of the design life and for ice class IC it is 1.6 %. In contrast, ice class IA Super and IA have no operational restrictions. This study can be used as a guide for the selection of an ice class.Description
Supervisor
Suominen, MikkoThesis advisor
Romanoff, JaniYu, Zhaolong
Keywords
ship structure, ice class, steel weight reduction, particle swarm optimisation
